Abstract: A heating apparatus includes a heating element having a conductor, at least a part of which is an electrically closed circuit along which an eddy current flows; a container for accommodating the heating element; a magnetic field induction section for induction-heating the heating element; and a high frequency power supply device for supplying high frequency power to the magnetic field induction section. The heating element is induction-heated by an AC magnetic field generated by the magnetic field induction section.

Abstract: A method of correcting an output waveform of a head includes the steps of (a) obtaining a sample error value of a sample value when subjecting an analog signal output from a head to an analog-to-digital conversion, and (b) correcting a vertical asymmetry of a waveform of the analog signal when carrying out he analog-to-digital conversion by changing a corresponding relationship between the analog signal and a digital signal which is obtained by the analog-to-digital conversion based on the sample error value. The step (b) calculates a correction value with respect to the analog-to-digital conversion based on the sample error value, and changes an input range of the analog-to-digital conversion to become vertically asymmetric depending on the correction value.

Abstract: A high-frequency inverter having a simple circuit construction capable of executing a constant-frequency operation and a zero-volt switching operation and an induction heating cooker using the high-frequency inverter are disclosed. The high-frequency inverter is comprised of an inverter circuit for converting a direct current from a DC power source into a high-frequency current and a control circuit for controlling the inverter circuit. The inverter circuit is comprised of: a one-transistor inverter constructed of a heating coil whose one terminal is connected to one terminal of a DC power source, a first switching element connected in series between the other terminal of the heating coil and the other terminal of the DC power source, and a first resonance capacitor connected so as to form a resonance circuit with the heating coil; and a series circuit connected in parallel with the heating coil and constructed of a second switching element and a second resonance capacitor.

Abstract: A switching device is employed in a power supply for driving a magnetron with lower withstand voltage and better controllability. A high frequency heating apparatus comprises a power supply, a leakage transformer connected to the power supply, a first switching device connected in series to a primary coil side of the leakage transformer, a first capacitor, a series circuit of a second capacitor and a second switching device, a driving circuit having an oscillator for driving the first switching device and the second switching device, a rectifier connected to a secondary coil side of the leakage transformer, and a magnetron connected to the rectifier. With this configuration, voltage applied to the first switching device can be clamped, and at the same time, the OFF time can be freely adjustable by the effect of the second capacitor and the second semiconductor switching device.

Abstract: A device for detecting a bending magnitude of a rotary shaft comprises a first pair of coils spaced from and facing the outer surface of a shaft and having an inductance value, and a second pair of coils spaced from and facing the outer surface of the shaft and connected in series to the first pair of coils at respective nodal points. The second pair of coils has an inductance value different from the inductance value of the first pair of coils. A pair of high frequency oscillators applies a high frequency voltage across the first and second pairs of coils to generate at each of the nodal points an output signal corresponding to a bending magnitude of the shaft, each output signal having a constant linearity characteristic resulting from the difference in inductance value between the first and second pairs of coils. An amplifier is connected to each of the nodal points for amplifying the output signals from the nodal points.

Abstract: In a switching device of an induction heating cooker, an oppositely poled diode for conducting a reverse current is coupled across the collector-emitter portion of a switching element provided in the first switching device, and turn-ON operation of the switching devices does not OCCUR in normal operation of the DUTY FACTOR T.sub.2 /T.sub.1 .apprxeq.0.5.

Abstract: An induction heating cooker has a rectifier (13) for producing pulsating DC current, an inverter (14) which receives the pulsating current given from the rectifier (13) and produces a high frequency output current and a load circuit (15) including an output coil (21) and a resonance capacitor (22) connected in series to each other to receive high frequency output signal from the inverter, and the variation or adjustment of output electromagnetic power is made by changing duty ratio of the high frequency output current of the inverter by giving variable duty ratio setting signals to switching elements (Qa, Qb) in the inverter 14; the frequency of the high frequency output current of the inverter 14 is fixed, and therefore, unpleasant interference sound is not generated at parallel simultaneous operation.

Abstract: The control system is provided in a grinding machine composed of an axially movable rotational shaft having a grinding tool and being supported magnetically by electromagnets. The control system includes a target position modifying controller for modifying or shifting a reference target levitating position of the rotational shaft in a retreating direction away from a workpiece reaches a predetermined amount. The control system further includes a rigidity modifying controller operative during quick feed operation of the rotational shaft for making a rigidity of the rotational shaft lower than that in the grinding operation by adjusting exciting currents of the electromagnets. The control system still further includes a dressing controller operative during dressing of a new grinding tool for detecting that the grinding tool begins to touch a dresser and for judging that the dressing is completed just when an arithmetic value calculated based on the detection reaches a predetermined value.

Abstract: A control system is provided in a grinding machine composed of an axially movable rotational shaft having a grinding tool and being supported magnetically by electromagnets. The control system includes a target position modifying controller for modifying or shifting a reference target levitating position of the rotational shaft in a retreating direction away from a workpiece reaches a predetermined amount. The control system further includes a rigidity modifying controller operative during quick feed operation of the rotational shaft for making a rigidity of the rotational shaft lower than that in the grinding operation by adjusting exciting currents of the electromagnets. The control system still further includes a dressing controller operative during dressing of a new grinding tool for detecting that the grinding tool begins to touch a dresser and for judging that the dressing is completed just when an arithmetic value calculated based on the detection reaches a predetermined value.

Abstract: A grinder with a deflection sensor for controlling the grinding work conditions based on an amount of deflection of a grinding shaft occurring in the normal direction relative to the grinding shaft which is detected by measuring inductance with the deflection sensor. Based on a deflection of the grinding shaft detected during grinding work, the feed of the grinder is controlled, and the sharpness of the grinder is determined based on changes of the detected deflection amount during spark-out, moreover an error in the signal from the deflection detector caused by a thermal change can be compensated, whereby grinding work is carried out under an optimum condition, and the grinding accuracy and efficiency are improved.

Abstract: An induction heating apparatus comprises a heating coil and a transistor which is connected to a direct current power source in series thereto to form an inverter for converting the direct current to an alternating current, and furthermore, a first coupling coil for supplying a forward base current to the transistor is coupled with the heating coil inductively and a second coupling coil for supplying a inverse base current for the transistor is also coupled to the heating coil inductively, and the inverter is controlled by a switching device which is controlled by a control circuit.